JP7740106B2 - Piezoelectric element, microphone, and method for manufacturing piezoelectric element - Google Patents

Description

The present invention relates to a piezoelectric element, a microphone, and a method for manufacturing a piezoelectric element.

Piezoelectric MEMS (Micro Electro Mechanical Systems) microphones are composed of a piezoelectric element with a layered structure of electrodes and piezoelectric film. In the manufacturing process for piezoelectric elements, a lower electrode is formed over the entire top surface of a substrate, and after a portion is removed by patterning, a piezoelectric film is formed on top of the lower electrode. An upper electrode is then formed on top of this piezoelectric film. A via is formed in the piezoelectric film to expose the lower electrode, and the potential of the lower electrode is extracted through wiring formed in this via. An opening is also formed in the substrate, and a slit is formed in the layered structure of the electrode and piezoelectric film, allowing this layered structure to be cantilevered at the open edge of the substrate and serve as a vibration region.

The piezoelectric film formed in the area where the electrode has been removed may have poor crystallinity, and stress concentration at the electrode edge may cause cracks and a decrease in resistance. If leakage occurs between the electrodes through the area with reduced resistance, dielectric loss increases, resulting in increased microphone noise, so it is necessary to block the leakage. An interlayer insulating film is typically used for this purpose (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 10-74836

In such microphones, the vibration area vibrates when pressure such as sound pressure is applied, and the charge generated in the piezoelectric film is output as a detection signal. However, residual stress generated during manufacturing can deform the vibration area, widening the slit and allowing pressure to escape, potentially narrowing the detection band. In response to this issue, the inventors proposed in Japanese Patent Application No. 2021-152427 a piezoelectric element that suppresses slit widening by forming an additional thin film within the slit.

However, forming an additional thin film increases the number of steps, which may increase the manufacturing cost of the piezoelectric element.

In view of the above, the present invention aims to provide a piezoelectric element, a microphone, and a method for manufacturing a piezoelectric element that can reduce the increase in labor costs.

To achieve the above object, the invention described in claim 1 provides a piezoelectric element having a vibration portion (20) disposed on a support (10), comprising a piezoelectric film (40) disposed on the support, an electrode film (50) laminated on the piezoelectric film, through-hole electrodes (61b, 62b) formed inside holes (61a, 62a) penetrating the piezoelectric film, and an interlayer insulating film (82) formed on the wall surfaces of the holes and on the top of the piezoelectric film to insulate the piezoelectric film from the through-hole electrodes. The vibration portion includes the piezoelectric film and the electrode film, and has a support region (21a) supported by the support and a floating region (21b) floating above the support. The floating region has multiple vibration regions (22a-22d) partitioned by slits (30), and an additional thin film (81) made of the same material as the interlayer insulating film is disposed in the slits.

As a result, because the additional thin film and the interlayer insulating film are made of the same material, they can be formed in the same process, reducing the number of steps required to manufacture piezoelectric elements.

In addition, in the invention described in claim 10 , there is provided a method for manufacturing a piezoelectric element having a vibration portion (20) arranged on a support (10), the method comprising the steps of forming a piezoelectric film (40) on the support, forming an electrode film (50) laminated on the piezoelectric film, forming holes (61a, 62a) penetrating the piezoelectric film, forming through electrodes (61b, 62b) inside the holes, forming an interlayer insulating film (82) on the wall surfaces of the holes and on the top of the piezoelectric film to insulate the piezoelectric film from the through electrodes, forming slits (30) in a floating region that includes the piezoelectric film and the electrode film and floats above the support, thereby dividing the piezoelectric film and the electrode film into a plurality of vibration regions (22a to 22d), and forming an additional thin film (81) made of the same material as the interlayer insulating film in the slit, wherein the forming of the interlayer insulating film and the forming of the additional thin film are performed simultaneously.

This allows the additional thin film and interlayer insulating film to be formed simultaneously using the same material, reducing the increase in labor costs.

Note that the reference symbols in parentheses attached to each component indicate an example of the correspondence between that component and the specific components described in the embodiments described below.

FIG. 2 is a plan view of the piezoelectric element according to the first embodiment. FIG. 2 is a cross-sectional view taken along line II-II of FIG. FIG. 2 is a plan view of the vicinity of the first and second holes. 5A to 5C are cross-sectional views showing a manufacturing process of a piezoelectric element. 4B is a cross-sectional view showing a manufacturing process of the piezoelectric element subsequent to FIG. 4A. 4C is a cross-sectional view showing a manufacturing process of the piezoelectric element subsequent to FIG. 4B. 4D is a cross-sectional view showing a manufacturing process of the piezoelectric element subsequent to FIG. 4C. 4D is a cross-sectional view showing a manufacturing process of the piezoelectric element subsequent to FIG. 4D. 4E is a cross-sectional view showing a manufacturing process of the piezoelectric element subsequent to FIG. 4E. 4F , a cross-sectional view showing a manufacturing process of the piezoelectric element following FIG. 4F . 4G ; FIG. FIG. 10 is a cross-sectional view of a comparative example. FIG. 10 is a cross-sectional view of a piezoelectric element according to a second embodiment. 5A to 5C are cross-sectional views showing a manufacturing process of a piezoelectric element. 7B is a cross-sectional view showing a manufacturing process of the piezoelectric element subsequent to FIG. 7A. 5A to 5C are cross-sectional views showing a manufacturing process of a piezoelectric element. 8B is a cross-sectional view showing a manufacturing process of the piezoelectric element subsequent to FIG. 8A. 5A to 5C are cross-sectional views showing a manufacturing process of a piezoelectric element. 9B is a cross-sectional view showing a manufacturing process of the piezoelectric element subsequent to FIG. 9A.

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that in the following embodiments, identical or equivalent parts will be denoted by the same reference numerals.

(First embodiment)
A first embodiment will be described. The piezoelectric element of this embodiment is suitable for use in a piezoelectric microphone mounted on a smartphone, an AI (artificial intelligence) speaker, etc. The piezoelectric element of this embodiment is also suitable for use in an ultrasonic sensor, etc.

As shown in Figures 1 and 2, the piezoelectric element comprises a support 10 and a vibrating part 20 disposed on the support 10, and has a rectangular planar shape. The support 10 has a support substrate 11 having one surface 11a, and an insulating film 12 formed on the one surface 11a of the support substrate 11. The support substrate 11 is made of, for example, a silicon substrate, and the insulating film 12 is made of, for example, an oxide film.

A recess 10a is formed in the support 10 to allow the inner edge of the vibrating section 20 to float. Therefore, the vibrating section 20 has a support area 21a arranged on the support 10, and a floating area 21b that is connected to the support area 21a and floats above the recess 10a. In this embodiment, the open end of the recess 10a facing the vibrating section 20 has a planar rectangular shape. Therefore, the entire floating area 21b has a planar rectangular shape.

Openings 12a and 20a are formed in the outer edge portions of the insulating film 12 and the vibrating portion 20, exposing the outer edge portions of the support substrate 11. The openings 12a and 20a facilitate the dicing process when manufacturing the piezoelectric element and are not necessarily required.

Slits 30 are formed in floating region 21b, penetrating the floating region 21b in the thickness direction. The slits 30 are formed so as to divide floating region 21b into four parts. Specifically, two slits 30 are formed, passing through the center of floating region 21b and extending toward opposite corners of floating region 21b. In other words, the slits 30 extend from each corner of floating region 21b, which has a rectangular planar shape, toward the center, and are formed so that each slit 30 intersects at the center. This separates floating region 21b into first to fourth vibration regions 22a to 22d, each of which has a roughly triangular planar shape.

In this embodiment, the slits 30 extend to the support region 21a, but may also be formed so as to terminate within the floating region 21b. Alternatively, the slits 30 may be formed so as to terminate at the boundary between the floating region 21b and the support region 21a.

By configuring the first to fourth vibration regions 22a to 22d as described above, the end on the support region 21a side is a fixed end, and the tip end on the opposite side to the support region 21a is a free end, forming a cantilever.

The vibrating section 20 is configured to include a piezoelectric film 40 and an electrode film 50 connected to the piezoelectric film 40. Specifically, the piezoelectric film 40 includes a lower piezoelectric film 41 and an upper piezoelectric film 42 laminated on the lower piezoelectric film 41. The lower piezoelectric film 41 and upper piezoelectric film 42 are made of lead-free piezoelectric ceramics such as scandium aluminum nitride (ScAlN) and aluminum nitride (AlN). The lower piezoelectric film 41 and upper piezoelectric film 42 are made of lead zirconate titanate (PZT). Although Figure 1 is not a cross-sectional view, the upper piezoelectric film 42 and other parts are hatched to facilitate understanding.

The electrode film 50 is formed on each vibration region 22a-22d so as to connect to the piezoelectric film 40, and is made of molybdenum (Mo). However, the electrode film 50 may also be made of a metal material whose main component is one of titanium (Ti), platinum (Pt), aluminum (Al), ruthenium (Ru), etc., in addition to molybdenum.

In this embodiment, the electrode films 50 include a lower electrode film 51 formed below the lower piezoelectric film 41, an intermediate electrode film 52 formed between the lower piezoelectric film 41 and the upper piezoelectric film 42, and an upper electrode film 53 formed above the upper piezoelectric film 42. The lower electrode film 51 and the intermediate electrode film 52 are arranged to face each other with the lower piezoelectric film 41 in between. The intermediate electrode film 52 and the upper electrode film 53 are arranged to face each other with the upper piezoelectric film 42 in between.

The electrode films 50 of the first to fourth vibration regions 22a to 22d are electrically connected in series by the wiring section 60. Specifically, the lower electrode films 51, intermediate electrode films 52, and upper electrode films 53 formed in each vibration region 22a to 22d are connected in parallel, while the vibration regions 22a to 22d are connected in series.

The wiring section 60 includes a first electrode section 61 connected to the lower-layer electrode film 51, a second electrode section 62 connected to the middle-layer electrode film 52, and a wiring film 63 connecting the first electrode section 61 and the second electrode section 62. The wiring section 60 also includes an electrode section (not shown) connected to the upper-layer electrode film 53, and the first electrode section 61 and the second electrode section 62 are also connected to this electrode section (not shown) via the wiring film 63.

A first hole 61a is formed in the support region 21a, penetrating the lower-layer piezoelectric film 41 and the upper-layer piezoelectric film 42 to expose the lower-layer electrode film 51. The first electrode portion 61 has a first through electrode 61b arranged in the first hole 61a so as to be electrically connected to the lower-layer electrode film 51. Furthermore, a second hole 62a is formed in the support region 21a, penetrating the upper-layer piezoelectric film 42 to expose the middle-layer electrode film 52. The second electrode portion 62 has a second through electrode 62b arranged in the second hole 62a so as to be electrically connected to the middle-layer electrode film 52.

As described below, an interlayer insulating film 82 is formed on the wall surfaces of the first hole 61a, the wall surfaces of the second hole 62a, and the top surface of the upper-layer piezoelectric film 42. The first through-hole electrode 61b and the second through-hole electrode 62b are disposed inside the first hole 61a and the second hole 62a, respectively, so as to be insulated from the piezoelectric film 40 by the interlayer insulating film 82. The wiring film 63 is disposed on the top surface of the interlayer insulating film 82 and is electrically connected to the first through-hole electrode 61b and the second through-hole electrode 62b above the first hole 61a and the second hole 62a. Note that FIG. 1 only illustrates the portion of the wiring film 63 that connects the first through-hole electrode 61a and the second through-hole electrode 62b, and the pad portion that is connected to an external circuit.

The vibration section 20 has a buffer layer 70 on the support 10 side, on which the lower piezoelectric film 41 and lower electrode film 51 are disposed. The buffer layer 70 is made of, for example, aluminum nitride (AlN). The buffer layer 70 is formed over the entire area that will become the floating region 21b. Note that the buffer layer 70 and lower electrode film 51 do not extend to the outer edge of the insulating layer 12. Therefore, the outer edge portion of the lower piezoelectric film 41 is disposed directly on the insulating film 12.

In the piezoelectric element of this embodiment, an additional thin film 81 is provided to cover a portion of the slit 30 formed in the floating region 21b. Specifically, the additional thin film 81 is disposed on the portion of the slit 30 opposite the support region 21a, i.e., the portion that defines the free end sides of the first to fourth vibration regions 22a to 22d. As a result, the vibration regions 22a to 22d are connected by the additional thin film 81 at their free end sides. Note that while Figure 2 shows the additional thin film 81 disposed so as to fill the slit 30, the additional thin film 81 does not have to be disposed so as to fill the slit 30.

The additional thin film 81 is intended to suppress warping of the first to fourth vibration regions 22a to 22d after the recess 10a is formed. The additional thin film 81 is preferably made of a material with a low Young's modulus so that it is less likely to affect the vibration of each vibration region 22a to 22d. The thickness of the additional thin film 81 is, for example, between 0.5 μm and 3 μm.

An interlayer insulating film 82 is formed on the wall surfaces of the first hole 61a and the second hole 62a. The interlayer insulating film 82 is intended to suppress leakage between the electrodes. The interlayer insulating film 82 is also formed on the upper surface of the upper piezoelectric film 42, and the first electrode portion 61 and the second electrode portion 62 are connected via a wiring film 63 formed on the upper surface of the interlayer insulating film 82. The interlayer insulating film 82 is made of the same material as the additional thin film 81. Specifically, the additional thin film 81 and interlayer insulating film 82 are made of a photosensitive resin such as polyimide or polybenzoxazole (PBO).

In the center of the piezoelectric element, an opening 82a is formed in the interlayer insulating film 82, thereby exposing the upper electrode film 53 in the floating region 21b from the interlayer insulating film 82. The opening 82a corresponds to the first opening. In addition, in the outer periphery of the piezoelectric element, openings 82b are formed in the interlayer insulating film 82, thereby exposing the upper piezoelectric film 42 in the support region 21a from the interlayer insulating film 82. The openings 82b correspond to the second opening. The openings 82b are linear slits, and four openings 82b are formed so as to be parallel to the four sides of the top surface of the piezoelectric element. The openings 82b may have other shapes.

The volume of the portion of the interlayer insulating film 82 formed between the first hole 61a and the opening 82a is equal to that of the portion formed on the opposite side of the first hole 61a from the opening 82a. Specifically, as shown in Figures 2 and 3, the region of the interlayer insulating film 82 between the first hole 61a and the opening 82a is designated as the inner region 82c, and the region between the first hole 61a and the opening 82b is designated as the outer region 82d, with the volumes of the inner region 82c and the outer region 82d being equal. Note that the wiring film 63 is not shown in Figure 3.

Furthermore, the portion of the interlayer insulating film 82 formed between the second hole 62a and the opening 82a and the portion formed on the opposite side of the second hole 62a from the opening 82a are made to have the same volume. Specifically, as shown in Figures 2 and 3, the region of the interlayer insulating film 82 between the second hole 62a and the opening 82a is called the inner region 82e, and the region between the second hole 62a and the opening 82b is called the outer region 82f, and the volumes of the inner region 82e and the outer region 82f are made to be equal.

The above is the configuration of the piezoelectric element in this embodiment. In such a piezoelectric element, when pressure such as sound pressure is applied to each of the vibration regions 22a to 22d, the vibration regions 22a to 22d vibrate. Then, for example, if the free end side of each of the vibration regions 22a to 22d is displaced upward, tensile stress is generated in the lower piezoelectric film 41, and compressive stress is generated in the upper piezoelectric film 42. Therefore, pressure such as sound pressure is detected by extracting charge from the pad portion of the wiring section 60. In this case, in this embodiment, the opening area of the slit 30 is reduced by the additional thin film 81. This makes it difficult for pressure to escape through the slit 30, allowing for a wider detection band.

Next, a method for manufacturing the piezoelectric element will be described with reference to Figures 4A to 4H. In this embodiment, an example is described in which a piezoelectric element is manufactured using a wafer-shaped support body 10. However, piezoelectric elements may also be manufactured using a support body 10 that has been divided into chip units in advance.

First, as shown in Figure 4A, a support 10 is prepared, in which an insulating film 12 is disposed on a support substrate 11. Note that the support 10 in Figure 4A is actually in the form of a wafer, in which multiple element configuration regions are integrated via dicing lines.

Next, as shown in FIG. 4B, a buffer layer 70 and a lower electrode film 51 are formed in this order on the support 10 and patterned into a predetermined shape using a mask (not shown). The buffer layer 70 and the lower electrode film 51 are patterned so that they are positioned in the area that will become the floating region 21b. The buffer layer 70 and the lower electrode film 51 are also patterned to include a portion that connects to the first through electrode 61b and a portion that faces the second through electrode 62b in the stacking direction of the support 10 and the vibration section 20.

The buffer layer 70 and lower electrode film 51 are formed by a typical sputtering method, CVD (Chemical Vapor Deposition) method, or the like. The lower piezoelectric film 41, intermediate electrode film 52, upper piezoelectric film 42, and upper electrode film 53, which will be described later, are also formed by a typical sputtering method, CVD method, or the like.

Next, as shown in Figure 4C, a lower piezoelectric film 41 and an intermediate electrode film 52 are deposited. Next, as shown in Figure 4D, an upper piezoelectric film 42 is deposited to form the piezoelectric film 40. Furthermore, an upper electrode film 53 is deposited and patterned into a predetermined shape using a mask (not shown), thereby forming the electrode film 50.

Next, as shown in FIG. 4E, etching is performed using a mask (not shown) to form a first hole 61a that exposes the lower electrode film 51, a second hole 62a that exposes the intermediate electrode film 52, and a slit 30 that exposes the insulating film 12. Furthermore, the piezoelectric film 40 located along the dicing line is removed to form an opening 20a, and the insulating film 12 is removed to form an opening 12a.

Next, as shown in FIG. 4F, photosensitive resin 80 is applied to the entire wafer so as to cover the support 10, piezoelectric film 40, electrode film 50, and buffer layer 70. Next, as shown in FIG. 4G, the photosensitive resin 80 is exposed to light using a mask (not shown), thereby removing the photosensitive resin 80 from the portions corresponding to the openings 82a, 82b, first hole 61a, and second hole 62a, thereby forming the additional thin film 81 and interlayer insulating film 82. At this time, openings 82a and 82b are formed so that the volumes of inner region 82c and outer region 82d are equal, and so that the volumes of inner region 82e and outer region 82f are equal.

Next, as shown in FIG. 4H, a metal film is deposited to fill the first hole 61a and the second hole 62a, thereby forming the first through-hole electrode 61b and the second through-hole electrode 62b. The metal film deposited on the interlayer insulating film 82 is then patterned to form the wiring film 63. This completes the wiring section 60.

Then, a mask (not shown) is placed as appropriate and etching is performed to form recesses 10a. The substrate is then divided into chips along the dicing lines. This produces the above-mentioned piezoelectric element, in which the vibration part 20 is arranged on the support 10.

In the present embodiment described above, the additional thin film 81 and the interlayer insulating film 82 are made of the same material. Therefore, as described above, the additional thin film 81 and the interlayer insulating film 82 can be formed in the same process, reducing the increase in man-hours required to manufacture the piezoelectric element.

Furthermore, the above embodiment can achieve the following effects:

(1) The portions of the interlayer insulating film 82 formed between the first and second holes 61a, 62a and the opening 82a have the same volume as the portions formed on the opposite side of the opening 82a from the first and second holes 61a, 62a. If the interlayer insulating film 82 is made of photosensitive resin, it shrinks when hardened. Therefore, if the volume of the interlayer insulating film 82 differs significantly on both sides of the first and second holes 61a, 62a, the interlayer insulating film 82 within the first and second holes 61a, 62a will be asymmetric, as shown in Figure 5. On the other hand, in a piezoelectric microphone, it is necessary to remove the interlayer insulating film 82 from the vibration region, and the formation of the opening 82a results in a significant difference in volume of the interlayer insulating film 82 on both sides of the first and second holes 61a, 62a. As a result, insulation performance is reduced on one side where the interlayer insulating film 82 is thinner, and on the other side where the interlayer insulating film 82 is thicker, coverage is poor when forming wiring metal due to the overhang structure, which could result in disconnections. In response to this, by making the volume of the interlayer insulating film 82 equal on both sides of the first and second holes 61a, 62a as described above, the symmetry of the interlayer insulating film 82 within the first and second holes 61a, 62a is improved, and insulation performance degradation and disconnections can be suppressed.

(2) An opening 82b exposing the piezoelectric film 40 is formed in the interlayer insulating film 82 on the side opposite the opening 82a relative to the first and second hole portions 61a and 62a. By forming the opening 82b in this manner, the volumes of the inner regions 82c and 82e and the outer regions 82d and 82f can be adjusted, preventing a decrease in insulation and disconnection.

(3) In the interlayer insulating film 82, the inner region 82c and the outer region 82d have the same volume, and the inner region 82e and the outer region 82f have the same volume. This improves the symmetry of the interlayer insulating film 82 within the first and second holes 61a and 62a, and prevents deterioration of insulation and disconnections.

(4) The additional thin film 81 and interlayer insulating film 82 are made of a photosensitive resin such as polyimide or PBO. Because the electrode thickness of a piezoelectric microphone is as thin as several tens of nanometers, if, for example, TEOS (tetraethoxysilane) is used as the interlayer insulating film 82, there is a risk that the electrode film 50 will be damaged when the interlayer insulating film 82 is patterned by etching. In contrast, by using a photosensitive resin for the additional thin film 81 and interlayer insulating film 82, the additional thin film 81 and interlayer insulating film 82 can be patterned by photolithography, thereby minimizing damage to the electrode film 50.

(5) The piezoelectric element has a bimorph structure in which a lower electrode film 51, a lower piezoelectric film 41, a middle electrode film 52, an upper piezoelectric film 42, and an upper electrode film 53 are stacked in this order. In a piezoelectric element with this configuration, the interlayer insulating film 82 can suppress leakage at the interface between the lower piezoelectric film 41 and the upper piezoelectric film 42.

(6) By using the piezoelectric element of this embodiment in a microphone, the microphone can be made low noise and have a wide frequency band.

Second Embodiment
The second embodiment will be described. This embodiment is different from the first embodiment in the configuration of the interlayer insulating film 82, but is otherwise similar to the first embodiment, so only the differences from the first embodiment will be described.

In this embodiment, the film thickness of the portion of the interlayer insulating film 82 formed between the first hole 61a and the opening 82a is different from that of the portion formed on the opposite side of the first hole 61a from the opening 82a. Specifically, as shown in FIG. 6, the region of the interlayer insulating film 82 between the first hole 61a and the outer edge of the interlayer insulating film 82 is defined as an outer region 82g, and a portion of the outer region 82g is thinned so that the volumes of the inner region 82c and the outer region 82g are equal.

Furthermore, the portion of the interlayer insulating film 82 formed between the second hole 62a and the opening 82a has a different film thickness from the portion formed on the opposite side of the second hole 62a from the opening 82a. Specifically, as shown in FIG. 6, the region of the interlayer insulating film 82 between the second hole 62a and the outer edge of the interlayer insulating film 82 is defined as an outer region 82h, and a portion of the outer region 82h is thinned so that the volumes of the inner region 82e and the outer region 82h are equal.

In this embodiment, after the step shown in FIG. 4F, as shown in FIG. 7A, the photosensitive resin 80 is exposed to a small amount of light using a mask 91 that exposes the portions of the outer regions 82g and 82h to be thinned. Then, as shown in FIG. 7B, the photosensitive resin 80 is exposed to a larger amount of light than in the step shown in FIG. 7A using a mask 92 that exposes the portions corresponding to the openings 12a and 20a, the first hole 61a, the second hole 62a, and the opening 82a. This forms an interlayer insulating film 82 in which portions of the outer regions 82g and 82h have been thinned.

This embodiment has the same configuration and operation as the first embodiment, and can therefore achieve the same effects as the first embodiment.

Furthermore, the above embodiment can achieve the following effects:

(1) The interlayer insulating film 82 has different film thicknesses in the inner regions 82c and 82d and the outer regions 82g and 82h. By varying the film thickness depending on the location, it is possible to adjust the volume without exposing the upper piezoelectric film 43, and the area protected by the interlayer insulating film 82 is wider, thereby suppressing damage to the piezoelectric element.

(Other embodiments)
The present invention is not limited to the above-described embodiments and can be modified as appropriate within the scope of the claims. It goes without saying that, in each of the above embodiments, the elements constituting the embodiments are not necessarily essential unless expressly stated as essential or clearly considered essential in principle. In each of the above embodiments, when numerical values such as the number, values, amounts, and ranges of components of the embodiments are mentioned, they are not limited to the specific numbers unless expressly stated as essential or clearly limited to a specific number in principle. In each of the above embodiments, when the shape, positional relationship, etc. of components are mentioned, they are not limited to the shape, positional relationship, etc. unless expressly stated or clearly limited to a specific shape, positional relationship, etc. in principle.

For example, in the first embodiment, the symmetry of the interlayer insulating film 82 in the first and second holes 61a and 62a can be improved and degradation of insulation properties can be suppressed not only in a configuration in which the inner regions 82c and 82e and the outer regions 82d and 82f have completely equal volumes, but also in a configuration in which they are approximately equal.

Furthermore, in the second embodiment, the symmetry of the interlayer insulating film 82 within the first and second hole portions 61a and 62a can be improved and degradation of insulation properties can be suppressed, not only in configurations in which the inner regions 82c, 82e and the outer regions 82g, 82h have completely equal volumes, but also in configurations in which they are approximately equal.

In addition, in the second embodiment, depending on the locations of the first and second holes 61a, 62a and the size of the opening 82a, the volumes of the inner regions 82c, 82e and the outer regions 82g, 82h may be made equal by thinning portions of the inner regions 82c, 82e.

Furthermore, in the second embodiment, the portions of the photosensitive resin 80 corresponding to the openings 12a and 20a may be exposed twice. That is, after the step shown in FIG. 4F, the photosensitive resin 80 is exposed using a mask 91 that exposes the portions corresponding to the openings 12a and 20a and the thinned portions of the outer regions 82g and 82h, and then the photosensitive resin 80 is exposed using a mask 92 as shown in FIG. 7B.

In the second embodiment, the photosensitive resin 80 may be exposed to light to form the additional thin film 81 and interlayer insulating film 82, as shown in FIGS. 8A and 8B. That is, after the step shown in FIG. 4F, the photosensitive resin 80 is exposed to a small amount of light using a mask 91 that exposes the portions corresponding to the openings 12a, 20a, the first hole 61a, the second hole 62a, and the opening 82a, as well as the thinned portions of the outer regions 82g and 82h. Next, the photosensitive resin 80 is exposed to a small amount of light, similar to that used in the step shown in FIG. 8A, or to a medium amount of light, using a mask 92 that exposes the portions corresponding to the openings 12a, 20a, the first hole 61a, the second hole 62a, and the opening 82a. Considering alignment errors, the method shown in FIGS. 7A and 7B is preferable to this method.

In the second embodiment, the photosensitive resin 80 may be exposed to light to form the additional thin film 81 and interlayer insulating film 82, as shown in Figures 9A and 9B. That is, after the step shown in Figure 4F, the photosensitive resin 80 is exposed to light using a mask 91 that exposes the portions corresponding to the openings 12a, 20a, and 82a and the thinned portions of the outer regions 82g and 82h. Next, the photosensitive resin 80 is exposed to light using a mask 92 that exposes the portions corresponding to the openings 12a, 20a, the first hole 61a, the second hole 62a, and the opening 82a.

REFERENCE SIGNS LIST 10 Support 20 Vibration part 30 Slit 40 Piezoelectric film 50 Electrode film 81 Additional thin film 82 Interlayer insulating film

Claims (13)

A piezoelectric element in which a vibration part (20) is disposed on a support (10),
a piezoelectric film (40) disposed on the support;
an electrode film (50) laminated on the piezoelectric film;
through electrodes (61b, 62b) formed inside holes (61a, 62a) penetrating the piezoelectric film;
an interlayer insulating film (82) formed on the wall surface of the hole and on the upper portion of the piezoelectric film, for insulating the piezoelectric film from the through electrode;
the vibration section includes the piezoelectric film and the electrode film, and has a support region (21a) supported by the support body and a floating region (21b) floating above the support body;
The floating region has a plurality of vibration regions (22a to 22d) divided by slits (30),
A piezoelectric element in which an additional thin film (81) made of the same material as the interlayer insulating film is disposed in the slit. A first opening (82a) exposing the vibration region is formed in the interlayer insulating film,
2. The piezoelectric element according to claim 1, wherein a second opening (82b) exposing the piezoelectric film is formed in a portion of the interlayer insulating film formed on the opposite side of the hole from the first opening. 3. The piezoelectric element according to claim 2 , wherein the additional thin film and the interlayer insulating film are made of a photosensitive resin. 4. The piezoelectric element according to claim 3 , wherein the photosensitive resin is polyimide or polybenzoxazole. 2. The piezoelectric element according to claim 1 , wherein the additional thin film and the interlayer insulating film are made of a photosensitive resin. 6. The piezoelectric element according to claim 5 , wherein the photosensitive resin is polyimide or polybenzoxazole. The piezoelectric film has a lower piezoelectric film (41) and an upper piezoelectric film (42),
7. A piezoelectric element as described in any one of claims 1 to 6, wherein the electrode film comprises a lower electrode film (51) formed below the lower piezoelectric film, an intermediate electrode film (52) formed between the lower piezoelectric film and the upper piezoelectric film, and an upper electrode film ( 53 ) formed above the upper piezoelectric film. A microphone comprising the piezoelectric element according to any one of claims 1 to 6 . A microphone comprising the piezoelectric element according to claim 7 . A method for manufacturing a piezoelectric element in which a vibration part (20) is disposed on a support (10), comprising the steps of:
forming a piezoelectric film (40) on the support;
forming an electrode film (50) laminated on the piezoelectric film;
forming holes (61a, 62a) penetrating the piezoelectric film;
forming a through electrode (61b, 62b) inside the hole;
forming an interlayer insulating film (82) on the wall surface of the hole and on the upper portion of the piezoelectric film to insulate the piezoelectric film from the through electrode;
forming slits (30) in a floating region that includes the piezoelectric film and the electrode film and is floating above the support, and dividing the piezoelectric film and the electrode film into a plurality of vibration regions (22a to 22d);
forming an additional thin film (81) made of the same material as the interlayer insulating film in the slit;
A method for manufacturing a piezoelectric element, wherein the formation of the interlayer insulating film and the formation of the additional thin film are carried out simultaneously. forming a first opening (82a) in the interlayer insulating film to expose the vibration region;
and forming a second opening (82b) exposing the piezoelectric film in a portion of the interlayer insulating film formed on the opposite side of the hole from the first opening. 12. The method for manufacturing a piezoelectric element according to claim 10 , wherein the additional thin film and the interlayer insulating film are made of a photosensitive resin. The method for manufacturing a piezoelectric element according to claim 12 , wherein the photosensitive resin is polyimide or polybenzoxazole.